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Fifty Years of Super Supersweet Corn: It Keeps Getting Better

Jerald “Snook” Pataky
Jerald “Snook” Pataky
Professor of Plant Pathology
Department of Crop Sciences
(217) 333-6606; j-pataky@illinois.edu

In the early 1950s, John Laughnan, a maize geneticist and UI professor, was investigating linkage between two genes: a1, which affects production of anthocyanin (purple pigmentation), and sh2, which causes kernels to be shrunken and shriveled. As he contemplated why kernels of the sh2 genotype were so shriveled, Laughnan discovered that the endosperm of sh2 kernels stored less starch and four to 10 times more sugar than endosperms of normal sweet corn or field corn. In 1953, Laughnan published his findings in Genetics and suggested to the sweet corn industry that the shrunken-2 allele may have application in commercial sweet corn hybrids. Few breeders shared Laughnan’s enthusiasm for this new type of “supersweet” corn, but 50 years later, his discovery and persistence have changed an entire industry.

Seeing an opportunity where others did not, Laughnan began to convert a few popular sweet corn inbreds to sh2. In 1961, he released through Illinois Foundation Seeds Inc. (IFSI) the supersweet versions of“Golden Cross Bantam” and “Iochief,” which became known as “Illini Chief.” Since seed of “Illini Chief” was difficult to produce, IFSI developed a three-way hybrid named “Illini Xtra Sweet.” Thus, IFSI became the first company to sell supersweet corn. Under the direction of Floyd Ingersoll, IFSI developed a significant market for their new corn in Japan. For the next 20 years, IFSI and Crookham Company, an Idaho-based seed company, were the only commercial companies with serious supersweet breeding programs. Emil Wolf at the University of Florida Everglades Station, Bob Andrews at the University of Wisconsin, and Jim Brewbaker at the University of Hawaii also were developing supersweet lines during this period.

As late as 1980, few commercial breeding programs were vigorously breeding supersweet corn, but most were enthusiastically adapting another type of high-sugar sweet corn developed at UI. The “sugary enhancer” traitwas discovered in the late 1960s by A. M. “Dusty” Rhodes, a UI professor of horticulture. IL 677a, an “se”- inbred line developed from a cross of Illinois sweet corn and Bolivian corn, had about twice as much sugar content as normal sweet corn, extremely tender kernels, and a creamy texture. High quality se-hybrids derived from IL 677a were somewhat less sweet but considerably more tender than the supersweet hybrids available at that time. Nevertheless, like normal sweet corn, sehybrids had a relatively short shelf-life because kernel sugars were converted to starch soon after harvest. Conversely, supersweet hybrids could retain their sweetness for more than a week, if refrigerated, because they lacked the enzyme responsible for this conversion.

In the early 1980s, Abbott and Cobb Inc., a midsized seed company, began a successful marketing campaign to educate wholesale produce buyers and Florida sweet corn growers about the superior extended shelf-life of supersweet corn. Within five years, sweet corn production in Florida went from less than 2 percent to over 90 percent supersweet. Soon, the same trend occurred throughout the U.S. for all sweet corn grown for long-distance shipping (in other words, sweet corn sold in grocery stores). Simultaneously, the introduction of a supersweet hybrid with traits necessary for processing marked the beginning of canned supersweet corn.

In the past 20 years, hundreds of supersweet and sugary enhancer hybrids have been introduced. Many have disease resistance derived from lines developed at UI. An se-breeding line developed by Rhodes and a student, Mark Mikel, was the primary source of resistance in sweet corn to maize dwarf mosaic virus. Various Rp-genes, which were discovered in the 1960s by UI maize pathologist and breeder Art Hooker, are the primary method by which common rust is controlled in sweet corn today. Resistance to northern leaf blight and Stewart’s wilt developed at UI also has been incorporated into many supersweet and se-hybrids.

Today, nearly all sweet corn sold in grocery stores is supersweet, and at least one major food processing company cans supersweet corn exclusively. In the past three years, IFSI, Crookham, and a few other companies have introduced “Xtra Tender” hybrids, a new type of supersweet sweet corn that combines the beneficial attributes of Laughnan’s sh2 allele and Rhodes’ se corn.“Xtra Tender” hybrids inherit high sugar content and long shelf-life from sh2 and tender pericarp and creamy texture from se. The development of these hybrids represents the most recent example of progress that has resulted from the commercial adaptation by the sweet corn industry of research discoveries made by UI faculty.

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